Giardia duodenalis is a microscopic, flagellated parasite that often calls the human and animal gut its home. In most cases, it coexists harmlessly with its host, and most infected pets and people show no signs of illness. However, when it becomes pathogenic, it can cause diarrhea, digestive issues or weightloss.

Cats can carry a pathogenic version of the gut parasite that also infects humans, but how common is it among pet cats, and how often do they harbor such strains?

A recent study investigated these questions by analyzing stool test data from 157,616 pet cats across 49 U.S. states and five Canadian provinces between March 2022 and August 2023.